I managed to figure it out late last night what the problems were. I am trying to tinker with the GUI and modify it. I am not familiar with Fluid and I couldn't find much documentation on it. Do you have any other documentation besides the one on the FLTK site?

Sorry, fluid's one of those things that's just kinda opaque - I've found very little decent documentation past the basic tutorial. Mainly I used fltk because it's super fast for prototyping, it's truly ripe for a wx re-write. I really don't like the basic tutorial much because it ends up on a huge spiral of opengl weird stuff and not an awful lot of fluid.

I am just trying to make a sleeker GUI that displays all the things that my car is capable of displaying. Seeing that FLTK is really too simplistic, I might just ditch it and use another language for it. Thanks for all the help. I will write to you if I have anything worthy of contributing.

I was partially using obdgui to teach myself fltk out of curiousity, and partially I wanted something thrown together really quickly. I'm actually leaning towards writing a new wx flavor myself - it just doesn't have graph or dial primitives, and I'm too lazy to write my own [so far]

Add Fl_Gauge?

I found this nice gauge class:http://www.kiwacan.co.nz/fltk/Fl_Gauge.html
and tested it out it works great. But I need help adding it into obdgui. The problem is that it is in h and cxx, but obdgui is in fl and the h and cxx files are generated automatically by Fluid. I found some hint here:http://embedded.centurysoftware.com/...-tutorial.html
and mimicked it by adding
#include ...
in the maindisplay.fl file via Fluid. But I don't know how to add the Fl_Gauge.cxx file other than putting it in the same directory as the maindisplay.fl file. I tried to build the project using NetBeans and sure enough it failed trying to link maindisplay.cxx.o due to "undefined" Fl_Gauge function calls. I am stuck. Please help. Thanks!

How to update values?

Thanks that helped!

Now to update the values I though I just add a line in the maindisplay.fl file settemp(float val) part near the end of the file but it behaves as if the value was set only once for the custom gauge in the beginning while all the other original gauges keeps updating to new values. What am I missing?

...
Now to update the values I though I just add a line in the maindisplay.fl file settemp(float val) part near the end of the file but it behaves as if the value was set only once for the custom gauge in the beginning while all the other original gauges keeps updating to new values. What am I missing?

OK finally figured it out. Somehow the custom gauge need to call the redraw() function. The fltk built in ones don't.